Conceptual study of a morphing winglet based on unsymmetrical stiffness

Morphing technology has the potential to increase aircraft performance. Among the morphing technologies, the morphing winglet is a promising solution due to its small size and large effect on the aerodynamics. Morphing winglets have to carry the spanwise aerodynamic loads, with low weight and small size. This makes the design of a reliable morphing structure of great importance to realize a morphing winglet.In this paper, a novel compliant structure is proposed based on the concept of unsymmetrical stiffness. The morphing winglet has to change its dihedral angle, and its stiffness has to be large enough to carry loads. While increasing the total stiffness, the allocation of the stiffness can be unsymmetrical, introducing deformation under a linear actuation force. If the total stiffness and its asymmetry are properly designed, the final deformation under both aerodynamic loads and actuation force can be optimized. The current study uses different composite layups of round corrugation structures to provide the stiffness asymmetry. A simplified model is developed to estimate the induced deformation and required actuation force. The deformation limit of the structure is also predicted using detailed finite element analysis.To demonstrate the application of the morphing structure, the baseline design of a regional twin turboprop airliner is generated. A worm and rack actuation mechanism is also designed. For performance analysis, the weight due to the morphing winglet and its actuation system is estimated. The influence of retrofitting the baseline design is investigated to obtain a trade-off design for the morphing structure.From the conceptual study, the simplified approach provides the basic properties of the morphing structure to retrofit the baseline aircraft, which highlights the feasibility of this novel concept although further study is still needed for its detailed design and analysis